I took a break from hardware and manufacturing concerns tonight and sat down to write some code. I probably should have worked on the USB bootloader, but instead I wrote a simple spectrum analysis function for the Ubertooth platform. Similar to other transceiver IC spectrum analyzers (like my IM-Me implementation), it tunes its receiver to one frequency at a time and records the received signal strength before hopping to the next frequency.
For now I'm just dumping a table of values to a file and plotting it with gnuplot. In the future perhaps a more sophisticated user interface could be built, maybe integrating with Mike Kershaw's Spectrum Tools or something like that. In this plot, you can see a busy 802.11g network on channel 1 (centered at 2412 MHz) and some Bluetooth traffic (a device performing an inquiry scan) throughout the band.
While testing this, I tried pushing the limits of the CC2400's tuning range for the first time. The device I tested functioned with its receiver tuned from 2268 to 2794 MHz. (The supported range is 2400 to 2483.) I didn't actually generate test signals to validate that it could see stuff throughout the entire range, but my guess is that it is usable across the whole tunable range but with degraded performance at the extremes.
The spectrum analysis code is available in the Ubertooth repository and will be included in the next release. Let me know if you do anything interesting with it. There are just a few days left to pick up one of the first batch of boards by making a pledge on Kickstarter.